Two days after Hurricane Sandy hit northeast U.S. coastal areas, power and communications outages are continuing to be a concern, especially in lower Manhattan.

Verizon posted a dramatic photo online early Wednesday showing the lobby of one of its primary Manhattan facilities flooded in two feet of water early Monday. The photo shows floodwater reaching up on a reception desk and several doorways.

Verizon also reported early Wednesday that it continues to have "significant issues" in lower Manhattan, and that it may take Con Edison a week to restore power to that area. Removing contaminated floodwater requires monitoring by environmental agencies, which will affect the amount of time required, Verizon said.

Verizon didn't offer details on service outages in its latest online update, but wired and wireless communications outages have been widespread across all the major carriers, from the Northeast coast to West Virginia, where Sandy caused a blizzard in the mountains. The outages have affected all four major wireless carriers -- Verizon Wireless, AT&T, Sprint and T-Mobile USA.

Mid-day Tuesday, New York users tweeted that they were seeing lines of people at neighborhood pay phones to make calls. Some data communications, including tweets, are easier to make when cellular networks are down or burdened by heavy use, according to the carriers.

Verizon has been posting regular updates, and Tuesday night said the storm surge had resulted in flooding at several Verizon facilities in lower Manhattan and other parts of the New York area, interrupting commercial and backup power at the sites, making them inoperable. In some cases, Verizon teams were unable to access those sites, Verizon said.

Two major network hubs critical to the nation's infrastructure in lower Manhattan have been operating on generator power due to the storm and flooding, Computerworld reported late Tuesday. The hubs, including one owned by Google, are used to provide network connections for telecommunications companies.

The Federal Communications Commission reported early Tuesday that about one-fourth of all cell sites in the 10-state area affected by the storm were out of service, as far west as Michigan. The FCC said the situation could worsen as some backup power supplies, including gasoline and diesel for generators, run out. A small number 911 call centers lost service, and calls were directed to other 911 facilities.

Nearly all cell towers and cellular antennas atop buildings rely primarily on power supplied by utility companies to run specialized computers called routers in shelters at the base of the towers. These base stations, which are about the size of a single-car garage, house racks of wireless routers and related gear. The base stations connect signals taken from antennas to wire or fiber cables that run underground to neighborhood and regional distributions centers, and from there to the rest of a global network.

During a power outage, wireless carriers usually provide backup with powerful batteries or emergency diesel generators. Some larger cell site locations, built with hurricane-strength walls and windows, have tanks of diesel on hand to power the generators for days or weeks.